The ultrathin carbon nanosheets (UCN) were effectively prepared from the industrial xylan through a sugar blowing method and a molten salt method in this study. The UCN prepared by the sugar blowing (BUCN) exhibited a 2–3-layer structure, which was similar to graphene carbon nano-layers, in contrast to the UCN prepared via the melt salt method, BUCN showed a lower density of surface defects, a larger specific surface area, and a more ordered layered structure, based on the results of the structures and morphologies of UCN. The ultrathin carbon nanosheets/nano-holocellulose composite films (CNH) and nano-holocellulose films were fabricated via vacuum filtration with different contents of BUCN and nano-holocellulose, and the structure, morphology, and properties were systematically investigated. The results showed that the CNH had good mechanical properties, UV screening effects, and thermal stability. The composite films became darker with a more obvious layered structure, and tensile strength and elongation at break increased with increasing UCN content. The resulting 70% UCN composite films, which retained 66.8% residual mass at 700 °C, exhibited strong peak current and rate performance in a three-electrode system with reversible charge–discharge reactions. Furthermore, the CNH presented shielding rates of 96.1% in the UVA and 98.1% in the UVB band. This study provides new insights into the low-cost industrial production and application of UCN and also paves the way for high-value utilization of biomass.
Zhang et al. (Thu,) studied this question.